The present invention is related broadly to the field of earth engineering equipment and more specifically to such equipment for lining upright shafts previously formed in the earth's surface.
In mining operation, central mining shafts, winding shafts, blind shafts, and ventilation shafts lead vertically downward from the earth's surface to and often beyond horizontal tunnels. Such shafts may extend from the earth's surface vertically downward to adjoining tunnels, or they may extend from one tunnel vertically to another tunnel at another elevation. Some vertical shafts, termed "blind shafts", extend downwardly from one tunnel to a closed bottom end. For mining purposes, nearly all vertical shafts must be lined with concrete or masonry to prevent the shaft walls from collapsing or "sloughing" and obstructing ventilation or otherwise isolating the adjoining horizontal tunnel.
During the drilling operation in which such upright shafts are formed, a liquid "drilling mud" may be utilized to assist the drilling operation and to prevent the shaft walls from sloughing onto the boring head. Ordinarily, the shaft is nearly completely filled with such drilling mud and must be pumped dry before conventional lining operations can take place.
Various apparatus and methods have been produced for placing shaft linings in upright dry excavations. Others show such apparatus for lining upright shafts that have been previously filled with "drilling mud". U.S. Pat. No. 4,031,708 granted to me on June 28, 1977 discloses a slipforming method and apparatus for in situ lining of an upwardly open shaft with monolithic concrete. This apparatus utilizes two conical shaped form members that receive wet concrete from an above ground source and spread it downward and outwardly against the walls of the shaft. The concrete is pumped from the above ground supply location and the slipform is intended to be moved upwardly within the shaft by receiving drilling mud from above the slipform and pumping it under pressure to the area below the slipform. Hydraulic pressure therefore serves to continuously move the slipform upwardly within the shaft.
U.S. Pat. No. 4,055,958 granted to me on Nov. 1, 1977 discloses another form of vertically moving slipform apparatus that receives wet concrete pumped under pressure from an above ground source. Again, two conical members receive the pumped concrete to direct it downwardly and outwardly against the shaft walls. In this particular application, however, the slipform is pulled upwardly as concrete is pumped from an above ground location to the vertically moving slipforms below. Another slipform apparatus is disclosed in my U.S. Pat. No. 4,067,675 issued on Jan. 10, 1978. This apparatus is designed to receive concrete under pressure from an above ground source and form it into a shaft lining while moving upwardly in the shaft due to the hydraulic pressure of the concrete being pumped. In other words, the wet, pumped concrete acts against the formed, partially hardened concrete, to push the slipform upwardly in the shaft.
While the above cited apparatus are effective, there is difficulty in controlling the concrete flow and slipform movement with power sources at the above ground location. It therefore becomes desirable to control the vertical slipform movement and delivery of concrete to the slipform within the slipform itself. This is especially true when large diameter linings are to be formed and the lining is to extend to a considerable depth. The weight of form members used to produce large diameter linings is extremely high and may cause strain on the usual form lifting equipment, especially when the shaft depth is considerable. If tension along lifting devices such as tremmie tubes, drilling rods, cables, etc. is to be held at an allowable level, and if accurate control of ascent is necessary, it becomes desirable to provide at least part of the lifting force through the slipform itself. Elongation of the lifting connectors would be held to a minimum, thereby decreasing the chance of damage due to stress and increasing accuracy of control.
Other form members utilized in lining upright shafts often incorporate a movement that is commonly known as "jump forming". This process has been reasonably effective but necessitates that the shaft be dry and drilled oversize in order to accommodate an outside form member for forming an outside surface of the lining. It further requires that workers be sent down the shaft in order to effectively operate the form members and spread the concrete evenly about the lining between an inside and outside form member. The danger of falling debris from sloughing shaft walls is ever present; plus the expense involved in labor is a prohibitive factor.
It therefore becomes desirable to obtain some form of slipform apparatus for forming a monolithic lining within preformed vertical shafts that may be operated to lift itself upwardly within the shaft. This is achieved as the lining is formed by pumping concrete directly from the slipform itself to maximize control of the slipform within the shaft regardless of its elevation therein. It is also desirable to obtain some type of slipform that may be "steered" within the shaft to accommodate shaft walls that are not completely vertical.